A new design of a coplanar-waveguide (CPW) feed for the excitation of a circularly polarized microstrip antenna is proposed. The proposed CPW feed has a 45°-inclined coupling slot and an inset tuning stub. Through the coupling slot, the electromagnetic energy can be coupled from the CPW feed line to the radiating patch, and fine tuning of good impedance matching is achieved by insetting a proper length of the tuning stub into the signal strip of the CPW feed line, resulting in a compact feed circuitry. By applying the proposed CPW feed to a circular patch with a bent tuning stub, a circularly polarized microstrip antenna can be achieved. Details of the antenna design and experimental results are presented and discussed.
Microwave Optical Technol. Lett. / vol.28, no.5, pp.311-312, Mar. 5, 2001, DOI: 10.1002/1098-2760(20010305)28:5<311::AID-MOP1027>3.0.CO;2-2